The present invention relates to an inkjet printer and a method of controlling the inkjet printer.
For example, an inkjet printer having the structure shown in FIG. 1 is conventionally known as an inkjet printer that performs positive pressure purging by causing compressed air generated by an air pump to act on the ink in an ink cartridge. Specifically, a head holder 101 is arranged so that it is movable in a reciprocating manner in a direction orthogonal to a direction of feeding recording paper A, and a print head 101A comprising a number of nozzles arranged in a plurality of lines is installed in the head holder 101. A plurality of ink cartridges 102M, 102C, 102B, and 102Y storing inks to be supplied to the print head 101A are provided, and also a plurality of pressure applying valves 103M, 103C, 103B, and 103Y are provided between the print head 101A and the respective ink cartridges 102M, 102C, 102B, and 102Y. A charge tank 105 for temporarily keeping the compressed air is provided between an air pump 104 and the ink cartridges 102M, 102C, 102B, and 102Y An atmospheric air release valve 107 is provided in an air channel 106 between the charge tank 105 and the respective ink cartridges 102M, 102C, 102B and 102Y, and switching means 108 for switching the ink cartridges 102M, 102C, 102B and 102Y to supply the compressed air is provided between the charge tank 105 and the ink cartridges 102M, 102C, 102B and 102Y. In an inkjet printer thus constructed, positive pressure purging is performed sequentially for a plurality of ink cartridges 102M, 102C, 102B, and 102Y by switching the ink cartridges 102M, 102C, 102B and 102Y to be supplied with compressed air by the switching means 108 and opening the pressure applying valves 103M, 103C, 103B and 103Y corresponding to the ink cartridges 102M, 102C, 102B and 102Y. After purging, the air pump 104 is stopped, and the atmospheric air release valve 107 is opened to release the compressed air remaining in the charge tank 105 to the atmosphere.
Moreover, there was proposed an inkjet recording apparatus in which a print head and a sub-tank unit are mounted on a carriage, and an ink cartridge connected to the print head through an ink supply tube, an air pump for supplying compressed air to the ink cartridge, a pressure regulator, a switching valve, etc. are provided in a printer main body (main body frame). In such an inkjet recording apparatus, when the amount of ink remaining in the sub-tank is small, the switching valve is switched to connect the air pump and an ink bag of the ink cartridge together, and therefore the compressed air in the air pump is supplied to the ink bag through the pressure regulator and the switching valve, and the ink in the ink bag is fed to the ink head and the sub-tank (see, for example, Japanese Patent Application Laid-Open No. 10-138506 (1998)).
However, in the ink jet printer shown in FIG. 1 and the inkjet recording apparatus described in Japanese Patent Application Laid-Open No. 10-138506 (1998)) mentioned above; the atmospheric air release valve and the pressure regulator are positioned between the air pump and the ink cartridge, and an air pressure adjustment of the compressed air to be supplied from the air pump to the ink cartridge is performed by the atmospheric air release valve and the pressure regulator. Therefore, a space for installing the large atmospheric air release valve and pressure regulator is required, and consequently not only the size of he inkjet printer becomes bigger, but also the production cost increases. Further, since the amount of compressed air that can be supplied to each ink cartridge is defined by the capacity of the pressure regulator placed on the upstream side of the ink cartridge, there is a possibility that a pressure force to be applied to the print head may vary depending on the amount of ink remaining in the ink cartridge.
Therefore, in order to simply adjust the pressure of the compressed air at low cost, in a known apparatus, an air supply tube for supplying the air from the air pump to an air chamber of each ink cartridge has an orifice, and the pressure is adjusted by discharging the compressed air generated in the air pump by the orifice when performing purging (see, for example, Japanese Patent Application Laid-Open No. 2004-58348).